# output.sourceMap

- **Type:**

```ts
type SourceMap = {
  js?: RspackConfig['devtool'];
  css?: boolean;
};
```

- **Default:**

```ts
const defaultSourceMap = {
  js: isDev ? 'cheap-module-source-map' : false,
  css: false,
};
```

- **Version:** `>= 0.2.0`

Used to set whether to generate source map files, and which format of source map to generate.

:::tip What is a source map
Source map is an information file that saves the source code mapping relationship. It records each location of the compiled code and the corresponding pre-compilation location. With source map, you can directly view the source code when debugging the compiled code.
:::

## Default Behavior

By default, the source map generation rules for Rsbuild are as follows:

- During development builds, source maps for JS files are generated for development debugging, while source maps for CSS files are not generated.
- During production builds, no source maps for JS and CSS files are generated to improve build performance.

## JS Source Map

The source map for JS files is controlled by `sourceMap.js` and can be configured by passing in all the source map formats supported by Rspack's [devtool](https://rspack.dev/config/devtool) option. Setting it to `false` will disable the source map.

For example, if you need to generate high-quality source maps in all environments, you can set it as follows:

```js
export default {
  output: {
    sourceMap: {
      js: 'source-map',
    },
  },
};
```

You can also set different source map formats based on the environment.

```js
export default {
  output: {
    sourceMap: {
      js:
        process.env.NODE_ENV === 'production'
          ? // Use a high quality source map format for production
            'source-map'
          : // Use a more performant source map format for development
            'cheap-module-source-map',
    },
  },
};
```

## CSS Source Map

The source map for CSS files is controlled by `sourceMap.css`. Setting it to `true` will enable the source map, while setting it to `false` will disable it.

For example, if you need to generate a source map for CSS files, you can set it as follows:

```js
export default {
  output: {
    sourceMap: {
      css: true,
    },
  },
};
```
